Hitherto, in an area lacking an adequate sewage system, general household wastewater is discharged untreated into the natural environment as it is. This is a great cause of environmental, disruption.
Under these circumstances, recently, a combined wastewater purifier has become known which comprises three tanks, i.e. a settling tank for receiving and settling wastewater, a septic tank (anaerobic settling tank), and an aerobic biological treatment tank.
However, the combined wastewater purifier is generally a large-sized wastewater purifier and needs a wide site for installation. In addition, it is necessary to provide a separate flush toilet wastewater purifier, or the like, as installed at present. Therefore, the combined wastewater purifier suffers from the problem that it costs a great deal.